In the art of commercial and industrial lighting fixtures such as disclosed, for example, in U.S. Pat. Nos. 3,246,135, 3,254,205, 3,609,337 and 3,610,915, it is desirable to provide for tightly sealing the fixture housing which receives the lamp element and the reflectors in order to avoid the seepage of dust, dirt and moisture into the housing and onto the lamp element and reflectors. As shown in above U.S. Pat. Nos. 3,246,135 and 3,609,337, one form of seal is provided by positioning a resilient gasket between the frame-like surface on the cast metal housing and the covering glass lens element which is retained by a surrounding cast metal frame. Due to the cast construction of the metal housings and frames and the difficulty of obtaining precisely parallel surfaces between each housing and frame, it is frequently difficult to obtain a positive, fluid-tight and dependable seal which prevents the seepage of dust and moisture into the lamp and reflector chamber.
It has also been found desirable to provide a high intensity commercial and industrial light fixture with means for conveniently changing the projected angle of the light from the fixture in order to change the area of illumination or to concentrate the projected light in a specified area. Furthermore, it has been found desirable to provide for conveniently constructing the light fixture in different sizes for different intensities of illumination and thus be able to accommodate electric lamp elements of different sizes or lengths.
It is apparent after carefully reviewing the disclosures of the above patents and of other prior art lighting fixtures such as disclosed in U.S. Pat. Nos. 1,873,392, 2,849,598 and 3,679,886, that none of the light fixtures which have been either constructed or proposed, provide all of the desirable features mentioned above.